Isolation And Identification Of Pathogens Of Asragalus Membrance Root And Screening Of Antagonistic Actiomycetes To The Pathogens

Astragalus membranaceus is perennial herbaceous plants, Widely producted in many places like Inner Mongolia, Shanxi, Gansu Heilongjiang, etc. It has been listed as national third level plants to protect. Since it has a variety of functions such as fill gas-solid table, water swelling, skin's rebuild, It has been widely used as a traditional medicinal plant. In recent years, with the expanding of Astragalus membranaceus' s cultivated area. many problem occurred, such as the rotation cycle shortened and continuous cropping area increased, The problem of Astragalus membranaceus disease increased year by year, Astragalus membranaceus root rot is one of the mainly reason Whitch seriously restrained the development of Astragalus membranaceus industry.The prevention methods of Astragalus membranaceus were mainly composed of physical and chemical methods. To targeted puts forward the prevention method to the root rot of Astragalus membranaceus by biological means. We get the disease Astragalus membranaceus sample from Gansu province Longxi city. Through the tissue separation, in vitro root inoculation, potted plant experiment method to separate and identificate of pathogenic bacteria. And do the biological control experiment with the actinomycetes seperated from the hexi corridor. Screening the actinomyces which has a strong inhibition activity to Astragalus membranaceus root rot disease,Then optimizate the culture conditions of the chosen strain, Striving to find a new way to prevent and control the Astragalus membranaceus root rot disease. The main results list follows:1?Five pathogenic bacteria strains isolated from Astragalus membranaceus root rot cause it disease were identifed, Through the cultued characteristics, microscopic morphology and rDNA ITS sequence analysis, a comprehensive appraisal and finally indentified three strains of them belong to Fusarium solani, 2 strains belong to Fusarium oxysporum..2?To get the strong antibacterial activity strain to Astragalus membranaceus root rot disease. The tablet confrontation, inhibition of mycelial growth methods had been used., The finally result of screeing from 172 actinomycetes which isolated from hexi corridor was that 23 of them have inhibitory activity, 8 strains among that have inhibitory activity to 5 strains of Astragalus membranaceus root rot disease. Which calculated as 4.7%. and with the mycelial growth methods 4 of them have a good activity.3?Comprehensive screening and early screening results obtained good strains DA4-4-1, and optimize the culture medium conditions. Finally results show that strain DA4-4-1 have a good inhibition result to two differents disease Fusarium oxysporum and Fusarium solani which mainly cause Astragalus membranaceus root rot disease. and the inhibition maximum diameter of them were 20.16 mm and 19.33 mm respectively. By the inhibition of mycelial growth method screening again.The most strong inhibition of DA4-4-1 strain to Fusarium oxysporum and Fusarium solani were 34.6% and32.4% respectively.4? Combing the morphology, culture characteristics, physiological and biochemical characteristics and 16 srDNA gene sequence to identify the theories of system development of the strain DA4-4-1, Preliminaryly identificate the strains DA4-4-1 as Streptomyces tuirus.of Streptomyces.5?The optimization conditions of single factor experiment results to strain DA4-4-1 shows that The optimum carbon source was maltose, the optimum nitrogen source was?NH₄?₂SO₄. The optimal culture medium conditions obtained by orthogonal experiment was maltose15 g/L,?NH₄?₂SO₄ 0.5 g/L, pH 7, NaCl 15 g/L, the inhibition rate of DA4-4-1 achieved to 86.72% to pathogen under the condition. The results shows that Antagonistic actinomycetes strain DA4-4-1 has a strong Inhibition activities, to Astragalus membranaceus root rot,and it has potential of biological control and application potential.6?Extraction of DA4-4-1 strain's filtered liquid.used three different extraction agent petroleum ether, ethyl acetate and butyl alcohol.Geting the result that the inhibition rate of it was 48.7%,So best extraction solvent is butyl acetate.